大约有 40,000 项符合查询结果（耗时：0.0487秒） [XML]
Why is iterating through a large Django QuerySet consuming massive amounts of memory?
...rst time you iterate over it. For example, this will print the headline of all entries in the database:
for e in Entry.objects.all():
print e.headline
So your ten million rows are retrieved, all at once, when you first enter that loop and get the iterating form of the queryset. The wait ...
CodeIgniter: Create new helper?
...o it.
<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
if ( ! function_exists('test_method'))
{
function test_method($var = '')
{
return $var;
}
}
Save this to application/helpers/ . We shall call it "new_helper.php"
The first line exists to ...
Installing older version of R package
...
To install an older version of a package from source (within R):
packageurl <- "http://cran.r-project.org/src/contrib/Archive/ggplot2/ggplot2_0.9.1.tar.gz"
install.packages(packageurl, repos=NULL, type="source")
If this doesn'...
Automatic vertical scroll bar in WPF TextBlock?
...g its vertical height. I expected a vertical scroll bar to appear automatically when that happens, but it didn't. I tried to look for a scroll bar property in the Properties pane, but could not find one.
...
How to prevent gcc optimizing some statements in C?
...eeds. This has the advantage of just applying to a single function and not all functions defined in the same file.
Usage example:
void __attribute__((optimize("O0"))) foo(unsigned char data) {
// unmodifiable compiler code
}
...
What does -D_XOPEN_SOURCE do/mean?
...ch one you need (if any) by looking at the man page for each function you call.
For example, man strdup says:
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
strdup(): _SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 500
strndup(), strdupa(), strndupa():...
What is the difference between typeof and instanceof and when should one be used vs. the other?
...
@Luke generally a bad idea to use "new String" like this. that creates a "string object" rather than a string primitive. see section here developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
– Colin D
...
How does one create an InputStream from a String? [duplicate]
...may not be the one you want here). For me, this is UTF-8 (which can encode all Java Strings). The right answer would be "indicate the encoding you really want", not "use UTF-16". And you can use it with .getBytes(charsetName), don't have to explicitly create a Charset object and encode the String to...
Multiple Updates in MySQL
...has new records then i will end up inserting only the ids and count except all other information. if and only if there is an entry for the id then it should update else it should skip. what shall i do?
– Jayapal Chandran
Aug 30 '10 at 13:30
...
Openssl is not recognized as an internal or external command
...
Well at the place of openssl ... you have to put actually the path to your openssl folder that you have downloaded. Your actual command should look like:
keytool -exportcert -alias androiddebugkey -keystore ~/.android/debug.keystore | "C:\Users\abc\openssl\bin\openssl.exe" sha1...